Summary

Cells regulate the destruction of proteins, just as they carefully regulate protein synthesis. Much of the proteolysis of cellular proteins occurs within a cylindrical organelle, the proteasome. Now Tamura et al. (p. 1385 of this issue) report the existence of a second new proteolytic organelle, the tricorn protease, in the bacteria Thermoplasma acidophilum. In their Perspective, Schneider and Hartl compare the structure and function of the proteasome and the tricorn protease.